package org.apache.lucene.document;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import org.apache.lucene.search.PrefixQuery;
import org.apache.lucene.search.RangeQuery;

import java.util.Date; // for javadoc

/**
 * Provides support for converting dates to strings and vice-versa. The strings
 * are structured so that lexicographic sorting orders by date, which makes them
 * suitable for use as field values and search terms.
 * 
 * <P>
 * Note that this class saves dates with millisecond granularity, which is bad
 * for {@link RangeQuery} and {@link PrefixQuery}, as those queries are
 * expanded to a BooleanQuery with a potentially large number of terms when
 * searching. Thus you might want to use {@link DateTools} instead.
 * 
 * <P>
 * Note: dates before 1970 cannot be used, and therefore cannot be indexed when
 * using this class. See {@link DateTools} for an alternative without such a
 * limitation.
 * 
 * @deprecated If you build a new index, use {@link DateTools} instead. This
 *             class is included for use with existing indices and will be
 *             removed in a future release.
 */
public class DateField {

	private DateField() {
	}

	// make date strings long enough to last a millenium
	private static int DATE_LEN = Long.toString(
			1000L * 365 * 24 * 60 * 60 * 1000, Character.MAX_RADIX).length();

	public static String MIN_DATE_STRING() {
		return timeToString(0);
	}

	public static String MAX_DATE_STRING() {
		char[] buffer = new char[DATE_LEN];
		char c = Character.forDigit(Character.MAX_RADIX - 1,
				Character.MAX_RADIX);
		for (int i = 0; i < DATE_LEN; i++)
			buffer[i] = c;
		return new String(buffer);
	}

	/**
	 * Converts a Date to a string suitable for indexing.
	 * 
	 * @throws RuntimeException
	 *             if the date specified in the method argument is before 1970
	 */
	public static String dateToString(Date date) {
		return timeToString(date.getTime());
	}

	/**
	 * Converts a millisecond time to a string suitable for indexing.
	 * 
	 * @throws RuntimeException
	 *             if the time specified in the method argument is negative,
	 *             that is, before 1970
	 */
	public static String timeToString(long time) {
		if (time < 0)
			throw new RuntimeException("time '" + time
					+ "' is too early, must be >= 0");

		String s = Long.toString(time, Character.MAX_RADIX);

		if (s.length() > DATE_LEN)
			throw new RuntimeException("time '" + time
					+ "' is too late, length of string "
					+ "representation must be <= " + DATE_LEN);

		// Pad with leading zeros
		if (s.length() < DATE_LEN) {
			StringBuffer sb = new StringBuffer(s);
			while (sb.length() < DATE_LEN)
				sb.insert(0, 0);
			s = sb.toString();
		}

		return s;
	}

	/** Converts a string-encoded date into a millisecond time. */
	public static long stringToTime(String s) {
		return Long.parseLong(s, Character.MAX_RADIX);
	}

	/** Converts a string-encoded date into a Date object. */
	public static Date stringToDate(String s) {
		return new Date(stringToTime(s));
	}
}
